1. Field of the Invention
The present invention relates to a switching power supply. More specifically, the present invention discloses an integrated circuit with an integrated power factor correction (PFC) circuit and MOSFET (Metal Oxide Semiconductor Field Effect Transistor) switch.
2. Description of the Prior Art
Power supplied to a system is one of the most determining factors in achieving a successful and high performing system. If the power is not of high quality, the overall system performance is affected and degraded.
There are many problems associated with power supply design that a designer must consider when developing a system.
Factors that must be considered are stability, controllability, reliability, and efficiency. After considering these factors, improving power quality must be addressed.
However, techniques to improve quality and performance often occupy excess space that is very valuable in compact systems.
Therefore, there is a need for a power factor correction circuit and MOSFET circuit integrated into a single IC therefore saving space and reducing costs while increase potential and frequency. Additionally, there is a need for a power factor correction circuit, a pulse width modulation control circuit, and MOSFET circuits integrated into a single IC, therefore saving additional space.
To achieve these and other advantages and in order to overcome the disadvantages of the conventional method in accordance with the purpose of the invention as embodied and broadly described herein, the present invention provides an integrated circuit with an integrated power factor correction (PFC) circuit and MOSFET switch and an integrated circuit with an integrated power factor correction (PFC) circuit, a pulse width modulation control (PWM) circuit, and MOSFET switch circuits.
An objective in modern power supply design is to provide the best quality of power to a system. However, there are many factors that can degrade the quality of this power and thus must be considered when developing a power supply system.
Generally, the power factor is defined as the ratio of total active power to total apparent power in volt-amperes in an ac circuit, where voltage and current are RMS values and include the effects of harmonics as well as the effects of phase displacement. If both voltage and current are sinusoidal, the power factor is the cosine of the angle between them.
However, in many applications, not only is the current waveform highly non-sinusoidal, but it is also out of phase with the voltage supply. Hence, these loads have a non-unity power factor, and draw reactive power.
To compensate these loads, a means to supply the reactive current at the appropriate times must be designed. A conventional approach utilizing a simple capacitor isn""t capable of doing this. A capacitor only compensates basic sinusoidal power factor lags, like those from linear inductors.
A technique of active power factor correction is to make the input to a power supply look like a simple resistor. Active power factor correction is capable of doing this by programming the input current in response to the input voltage. As long as the ratio between the voltage and current is constant, the input will be resistive thus making the power factor equal to 1. If the ratio is not constant, the input will contain phase displacement or distortion. This will degrade the power factor thus degrading the performance or quality of the power and system.
Therefore, a power factor correction technique is used to increase the power factor so that the phase angle between the voltage and current approaches zero in a circuit.
As mention previously, the quality of the power is important. High quality DC current is smooth and constant with very low ripple or noise. However, current derived from AC sources often contains ripple. Ripple is significant because it can affect the performance of the total system.
Pulse width modulation is a power conversion technique which converts AC voltage to a lower voltage DC signal. Pulse width modulation basically controls the duty cycle as well as the frequency of the power.
An object of pulse width modulation (PWM) control circuits is to filter the output to provide a smooth power. The frequency of the pulse width modulation control circuit is controlled to maintain a continuous smooth output voltage.
The present invention provides a power factor correction circuit (PFC) and a MOSFET circuit integrated into a single IC, therefore saving space and reducing costs while increase potential and frequency. Therefore, signals provided by the present invention ensure a smooth and high quality power to the system, thus improving the quality and performance of the overall system.
In an embodiment of the present invention, the integrated circuit further comprises a reference voltage circuit which provides a VREF output.
Another embodiment of the present invention provides a power factor correction circuit, a pulse width modulation control circuit, and MOSFET circuits integrated into a single IC.
The power factor correction circuit comprises an IAC input, a VRMS input, an ISENSE input, a RAMP1 input, a VFB input, VEAO output, an IEAO output, and a PFC-DRV output.
The IAC input and VRMS input supply input signals to the power factor correction circuit.
The ISENSE input is utilized by the power factor correction circuit to detect and limit the current to the power factor correction circuit. If the current is not within the desired range, the PFC-DRV output will be held low or shut off, thus protecting the integrity of the power factor correction circuit and the MOSFET circuit.
The power factor correction circuit further comprises a low power detection circuit, a VCC over-voltage protection circuit, a PFC over-voltage protection circuit, and a PFC current limiting circuit. The outputs of these protection circuits are logically considered so that if any one of these circuits detects one of these undesirable conditions, the PFC-DRV output of the power factor correction circuit is held low or switched off.
The MOSFET circuit is connected to the PFC-DRV output of the power factor correction circuit. The output of the MOSFET circuit is provided as PFCOUT.
The pulse width modulation control circuit comprises a RAMP2 input, a VDC input, an SS input, a DCILIMIT input, and a PWM-DRV output.
The VDC input, VFB input, and VCC input supply input signals to the pulse width modulation control circuit.
The DCILIMIT input is utilized by the pulse width modulation control circuit to detect and limit the current to the pulse width modulation control circuit. If the current is not within the desired range, the PWM-DRV output will be held low or shut off, thus protecting the integrity of the pulse width modulation control circuit and the MOSFET circuit.
The pulse width modulation control circuit further comprises a duty cycle limit circuit, a VIN OK circuit, a DC current limit circuit, and an under-voltage circuit. The outputs of these circuits are logically considered and if an undesirable condition is encountered, the PWM-DRV output of the pulse width modulation control circuit is held low or switched off.
The MOSFET circuit is connected to the PWM-DRV output of the pulse width modulation control circuit. The output of the MOSFET circuit is provided as PWMOUT.
The present invention provides a power quality correction circuitry integrated into a single IC, therefore saving space and reducing costs while increase potential and frequency. Therefore, signals provided by the present invention ensure a smooth and high quality power to the system, thus improving the quality and performance of the overall system.
These and other objectives of the present invention will become obvious to those of ordinary skill in the art after reading the following detailed description of preferred embodiments. It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.